74,973 research outputs found
A cusp electron gun for millimeter wave gyrodevices
The experimental results of a thermionic cusp electron gun, to drive millimeter and submillimeter wave harmonic gyrodevices, are reported in this paper. Using a "smooth" magnetic field reversal formed by two coils this gun generated an annular-shaped, axis-encircling electron beam with 1.5 A current, and an adjustable velocity ratio alpha of up to 1.56 at a beam voltage of 40 kV. The beam cross-sectional shape and transported beam current were measured by a witness plate technique and Faraday cup, respectively. These measured results were found to be in excellent agreement with the simulated results using the three-dimensional code MAGIC
Generation of high-energy monoenergetic heavy ion beams by radiation pressure acceleration of ultra-intense laser pulses
A novel radiation pressure acceleration (RPA) regime of heavy ion beams from
laser-irradiated ultrathin foils is proposed by self-consistently taking into
account the ionization dynamics. In this regime, the laser intensity is
required to match with the large ionization energy gap when the successive
ionization of high-Z atoms passing the noble gas configurations [such as
removing an electron from the helium-like charge state to
]. While the target ions in the laser wing region are ionized
to low charge states and undergo rapid dispersions due to instabilities, a
self-organized, stable RPA of highly-charged heavy ion beam near the laser axis
is achieved. It is also found that a large supplement of electrons produced
from ionization helps preserving stable acceleration. Two-dimensional
particle-in-cell simulations show that a monoenergetic beam
with peak energy and energy spread of is obtained by
lasers at intensity .Comment: 5 pages, 4 figure
Deterministic Quantum Key Distribution Using Gaussian-Modulated Squeezed States
A continuous variable ping-pong scheme, which is utilized to generate
deterministically private key, is proposed. The proposed scheme is implemented
physically by using Gaussian-modulated squeezed states. The deterministic way,
i.e., no basis reconciliation between two parties, leads a two-times efficiency
comparing to the standard quantum key distribution schemes. Especially, the
separate control mode does not need in the proposed scheme so that it is
simpler and more available than previous ping-pong schemes. The attacker may be
detected easily through the fidelity of the transmitted signal, and may not be
successful in the beam splitter attack strategy.Comment: 7 pages, 4figure
Regularity estimates for the gradient flow of a spinorial energy functional
In this article, we establish certain regularity estimates for the spinor flow introduced and initially studied in \cite{AWW2016}. Consequently, we obtain that the norm of the second order covariant derivative of the spinor field becoming unbounded is the only obstruction for long-time existence of the spinor flow. This generalizes the blow up criteria obtained in \cite{Sc2018} for surfaces to general dimensions. As another application of the estimates, we also obtain a lower bound for the existence time in terms of the initial data. Our estimates are based on an observation that, up to pulling back by a one-parameter family of diffeomorphisms, the metric part of the spinor flow is equivalent to a modified Ricci flow
Structural and vibrational properties of two-dimensional nanolayers on Pd(100)
Using different experimental techniques combined with density functional
based theoretical methods we have explored the formation of
interface-stabilized manganese oxide structures grown on Pd(100) at
(sub)monolayer coverage. Amongst the multitude of phases experimentally
observed we focus our attention on four structures which can be classified into
two distinct regimes, characterized by different building blocks. Two
oxygen-rich phases are described in terms of MnO(111)-like O-Mn-O trilayers,
whereas the other two have a lower oxygen content and are based on a
MnO(100)-like monolayer structure. The excellent agreement between calculated
and experimental scanning tunneling microscopy images and vibrational electron
energy loss spectra allows for a detailed atomic description of the explored
models.Comment: 14 pages, 11 figure
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